Blade assembly for rotary lawn mower

ABSTRACT

An arm and blade assembly for a rotary lawn mower is provided comprising an arm member defining a pair of arms, and a pair of blades, one affixed at the end of each arm, the blades being affixed to the arms by means of a keystone or dovetail joint providing restriction with respect to longitudinal and lateral movement, and a sleeve disposed over the joint providing restriction with regard to vertical movement, thereby providing a safe and positive means for readily affixing and detaching the blades to and from the arms.

United States Patent Staines [54] BLADE ASSEMBLY FOR ROTARY LAWN MOWER[72] Inventor: Harvey C. Staines, RR. 6, Box

1059, Battle Creek, Mich. 49017 [22] Filed: Nov. 12, 1970 [21] Appl.No.: 88,753

[52] US. Cl ..56/295 [51] Int. Cl. ..A0ld 55/18 [58] Field of Search..56/295, 255

[56] References Cited UNITED STATES PATENTS 2,232,261 2/1941 Orr..56/255 2,477,442 7/ 1949 Cramer, Jr. et al ..56/295 X 3,321,894 5/1967lngram ..56/295 1 Aug. 15,1972

Primary Examiner-Louis G. Mancene Assistant Examiner-J. N. EskovitzAttorney-Roy A. Plant [5 7] ABSTRACT An arm and blade assembly for arotary lawn mower is provided comprising an arm member defining a pairof arms, and a pair of blades, one afiixed at the end of each arm, theblades being afiixed to the arms by means of a keystone or dovetailjoint providing restriction with respect to longitudinal and lateralmovement, and a sleeve disposed over the joint providing restrictionwith regard to vertical movement, thereby providing a safe and positivemeans for readily affixing and detaching the blades to and from thearms.

9 Claims, 7 Drawing Figures Patented Aug. 15, 1972 2 Sheets-Sheet 1INVENTOR ATTORNEY Patented Aug. 15, 1972 3,683,606

2 Sheets-Sheet 2 INVENTOR A ORNEY BLADE ASSEMBLY FOR ROTARY LAWN MOWERBACKGROUND OF THE INVENTION The present invention deals broadly withlawn mower blades, and is more particularly concerned with an arm andblade assembly for a rotary motor which is relatively inexpensive toproduce, which is easy to fabricate, wherein blades may be readilymounted and dismounted, and which is yet safe in operation.

Rotary-tape lawn mowers have become extremely popular because of themany advantages they offer. They are simple to operate, they can beutilized to cut to the edge of a lawn and therefore obviate the need forsubsequent trimming, and are relatively inexpensive to build. Moreover,the blades may be readily removed for sharpening and quickly replaced.However, because of the extremely high speeds at which the bladesrotate, special care must be utilized in their design to insure that theblades are securely held by the rotating arm even when they accidentallystrike a hard stationary object.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide an arm and blade assembly for a rotary lawn mower which providesefficient cutting operation.

It is still further an object to provide an improved means whereby theblades are readily affixed to the ends of the arms, and readily somaintained during use.

It is an additional object to provide an assembly of the type describedwherein the blades may be readily detached from the supporting arms forsharpening, and

readily remounted.

It is still further an object to provide an assembly of the typedescribed which is relatively simple and inexpensive to manufacture.

Still further objects and advantages of the invention will appear as thedescription proceeds.

To the accomplishment of the foregoing and related ends, the invention,then, consists of an am and blade assembly for a rotary lawn mower, asherein fully described and particularly pointed out in the claims, theannexed drawings and the following description setting forth in detailcertain illustrative embodiments of the invention, such disclosedembodiments illustrating, however, but several of the various ways inwhich the present invention may be used.

BRIEF DESCRIPTION OF THE DRAWINGS In the annexed drawings:

FIG. 1 is a perspective view of an arm and blade assembly according tothe present invention.

FIG. 2 is a fragmentary top view showing the joint formed between ablade and the end of an arm before a sleeve is placed thereover forlocking in place.

FIG. 3 is a fragmentary view, partially in cross-section, taken at theline III-III of FIG. 4, looking in the direction of the arrows, andshowing the sleeve of the assembly in place.

FIG. 4 is a cross-sectional view taken at the line IV- IV of FIG. 3,looking in the direction of the arrows.

FIG. 5 is a view partially in cross-section of another embodiment of theinvention.

FIG. 6 is a cross-sectional view taken at theline VI- VI of FIG. 5,looking in the direction of the arrows.

FIG. 7 is a fragmentary top view of still another embodiment of theinvention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS FIG. 1 illustrates an arm andblade assembly 10 having an arm member 11 provided with a mounting hole12 for affixing the blade to a motor shaft. The arm member 11 has a pairof arms 13 and 14 to which blades 15 and 16 having cutting edges 17, 18,19 and 20 are affixed.

Referring more particularly to FIGS. 2-4, the means by which the blades15 and 16 are affixed to the arms 13 and 14 is shown in detail, andcomprises a keystone or dovetail tongue 29 provided as an extension ofthe blade and a complementary slot 21 provided at the end of the arm 14.The tongue 29 and slot 21 are so arranged that both longitudinal andlateral relative movement between the blade 16 and arm 14 arerestricted. In order to restrict vertical movement, sleeves 22 and 23are slidably mounted on the arm, and as shown in FIGS. 1, 3 and 4, areslidably moved until they cover the dovetail joint between the tongue 29and slot 21, the knife blade 16 now being completely and positivelyaffixed to the end of the arm 14. The sleeves 22 and 23 are sodimensioned that they provide a tight fit over the tongue to preventslipping. Additionally, the centrifugal force resulting from rotation ofthe arm member 11 maintains the sleeve in locked position. If desired,as shown in FIG. 7, detent means may be provided in the form of dimples24 and complementary detent depressions 25, which detent means cooperateto prevent the sleeve from slipping once it has been applied in place.If desired, the sleeves 22 and 23 can be manufactured from a singlestrip of metal, as shown in FIG. 4, with the free edges 26 and 27affixed together by means of a weld 28. As a safety measure the width ofthe blade 16 in the vicinity of the end where it engages the ends of thearm 14 should be greater than the inner width of the sleeve 23, therebyinsuring that the sleeve cannot be thrown off by thecentrifugal forcewhich develops due to rotation of the arm member 1 1.

Although in the preferred form of the invention, the tongue 20 is anintegral extension of the blade 16, the relationship can be reversed, asshown in FIGS. 5 and 6. In this embodiment the blade 31 comprisescutting edges 32 and 33 similar to those of the embodiment previouslyshown and described. However, here the arm 34 is provided with a tongue35 as an extension thereof, and the blade 33 is provided with acomplementary slot 36. The operation, however, is substantially the sameas in the previous embodiment, with the sleeve 37 placed over the tongueand slot combination to affix the blade and arm together with respect torelative movement in all directions. Additionally, as-shown in FIGS. 5and 6, the tongue 35 is provided with ribs 38 to prevent the sleeve 37from sticking to the tube 37 as a result of corrosion. Alternatively theblades, arm members or sleeves may be anodized or otherwise treated toprevent sticking of the various parts to each other due to corrosion.

Although the tongue and slot combination has been shown in theembodiments above in the form of a keystone or dovetail joint, othersuitable shapes may be utilized. FIG. 7 illustrates an embodimentcomprising a blade 40 having cutting edges 41 and 42 and a tongue 43which is curvilinear in this case. The arm 44 is provided with acomplementary slot 45 engaging the tongue 43. The assembly is completedby a sleeve 46 which may be slid over the tongue 43 to maintain it inplace.

In addition to the several forms which the tongue may take, asillustrated and described, various other forms may be used, as forexample, T-shaped, heartshaped, diamond-shaped, and any of a largevariety of shapes. It is only necessary that for the purpose ofproviding both lateral and longitudinal restraint, the complementarymember be provided with a slot so that the tongue be substantiallysurrounded, and additionally, that a portion of the tongue distal withrespect to its attachment to the member to which it is connected bewider than a portion which is proximal thereto.

The lawn mower arm and blade assembly of the present invention has anumber of advantages over the prior art assemblies. First, it is verysimple to remove and attach the blades to the arms. Second, a verypositive coupling means is provided which is safe to use. Further, theassembly may be very inexpensively and relatively simply produced.

While but only a few forms of the invention have been shown anddescribed, other forms will now be apparent to those skilled in the art.Therefore, the embodiments shown in the drawings are merely forillustrative purposes, and are not intended to limit the spirit andscope of the invention as above described and illustrated in thedrawings.

Other modes of applying the principle of my invention may be employed,instead of the ones explained, change being made as regards theapparatus herein disclosed, provided the features stated by any of thefollowing claims or the equivalent of such stated features be employed.

1 therefore particularly point out and distinctly claim as my invention:

1. An arm and blade subassembly for a rotary-type lawn mower, comprisingan arm member adapted to be mounted on a shaft, a detachable bladehaving at least one cutting edge, and means for affixing said blade tothe end of said arm comprising a tongue extending longitudinally as anintegral part of one member of said blade and said arm end and acomplementary slot provided in the other of said members, said tongueand slot being shaped to prevent relative longitudinal movement betweensaid arm end and said blade, and a sleeve slidably mounted on said armand adapted to be placed over said tongue and slot to confine saidtongue within said slot, wherein longitudinal ribs are provided on thesurface of said tongue to prevent corrosive adhesion to said sleeve.

2. An arm and blade subassembly according to claim 1, wherein saidtongue comprises an extension of said blade and said slot is provided insaid arm end.

3. An arm and blade subassembly according to claim 1, wherein saidtongue comprises an extension of said arm end and said slot is providedin said blade.

4. An arm and blade subassembly according to claim 1, wherein saidtongue has a dovetail shape.

5. An arm and blade subassembly according to claim 1, wherein saidtongue is curvilinear in shape.

6. An arm and b ade subassembly according to claim 1, wherein said bladehas two cutting edges and is adapted to be reversed for alternativelypresenting each cutting edge in the forward direction of rotation.

7. An arm and blade subassembly according to claim 1, wherein thesurfaces of said arm are treated to prevent corrosive adhesion to saidsleeve.

8. An arm and blade subassembly according to claim 7, wherein saidtreatment is anodizing.

9. A detachable blade having at least one cutting edge and adapted to bemounted at the end of a rotatable arm ofa rotary lawn mower, and meansfor affixing said blade to the end of said arm comprising a tongueextending as an integral part of one member of said blade and said armend, and a complementary slot provided at the end of the other member,said tongue and slot being shaped to prevent relative longitudinalmovement between said arm end and said blade, a sleeve slidably mountedon said arm and adapted to be placed over said tongue when engaged insaid slot, thereby confining said tongue within said slot, wherein saidtongue is provided with longitudinal ribs to prevent corrosive adhesionof said tongue to said sleeve.

August 15, 1972 Dated Patent No.

Inventofls) ha; error appears in the above-identified patent It iscertified t and that said Letters Patent are hereby corrected as FBIshown Below:

Column 1, line 11, for "Rotary-tape" read --Rotary-tyipe--..

Signed and sealed this 29th day of May 1973.

(SEAL) Attest:

EDWARD ,P TCHER,JR. ROBERT GOTTS CHALK Attesting Officer Commissioner ofPatents

1. An arm and blade subassembly for a rotary-type lawn mower, comprisingan arm member adapted to be mounted on a shaft, a detachable bladehaving at least one cutting edge, and means for affixing said blade tothe end of said arm comprising a tongue extending longitudinally as anintegral part of one member of said blade and said arm end and acomplementary slot provided in the other of said members, said tongueand slot being shaped to prevent relative longitudinal movement betweensaid arm end and said blade, and a sleeve slidably mounted on said armand adapted to be placed over said tongue and slot to confine saidtongue within said slot, wherein longitudinal ribs are provided on thesurface of said tongue to prevent corrosive adhesion to said sleeve. 2.An arm and blade subassembly according to claim 1, wherein said tonguecomprises an extension of said blade and said slot is provided in saidarm end.
 3. An arm and blade subassembly according to claim 1, whereinsaid tongue comprises an extension of said arm end and said slot isprovided in said blade.
 4. An arm and blade subassembly according toclaim 1, wherein said tongue has a dovetail shape.
 5. An arm and bladesubassembly according to claim 1, wherein said tongue is curvilinear inshape.
 6. An arm and blade subassembly according to claim 1, whereinsaid blade has two cutting edges and is adapted to be reversed foralternatively presenting each cutting edge in the forward direction ofrotation.
 7. An arm and blade subassembly according to claim 1, whereinthe surfaces of said arm are treated to prevent corrosive adhesion tosaid sleeve.
 8. An arm and blade subassembly according to claim 7,wherein said treatment is anodizing.
 9. A detachable blade having atleast one cutting edge and adapted to be mounted at the end of arotatable arm of a rotary lawn mower, and means for affixing said bladeto the end of said arm comprising a tongue extending as an integral partof one member of said blade and said arm end, and a complementary slotprovided at the end of the other member, said tongue and slot beingshaped to prevent relative longitudinal movement between said arm endand said blade, a sleeve slidably mounted on said arm and adapted to beplaced over said tongue when engaged in said slot, thereby confiningsaid tongue within said slot, wherein said tongue is provided withlongitudinal ribs to prevent corrosive adhesion of said tongue to saidsleeve.